1. Field of the Invention
This invention relates generally to computer storage and more particularly to a low current magnetic random access memory using a write magnet.
2. Description of the Related Art
The use of personal computers has expanded remarkably in recent years. As such, long-term computer data storage devices, such as hard disk, have become increasingly important to computer users. To keep up with demand for improved long-term computer data storage, Magnetic Random Access Memory (“MRAM”) has been developed. MRAM is a non-volatile memory that can be utilized for long-term data storage. MRAM devices perform read and write operations orders of magnitude faster than can be performed using conventional long-term storage devices such as hard drives. In addition, MRAM devices are more compact and consume less power than other conventional long term storage devices.
A typical MRAM device includes an array of memory cells. Word lines extend along rows of the memory cells, and bit lines extend along columns of the memory cells. Each memory cell is located at a cross point of a word line and a bit line. A memory cell stores a bit of information as an orientation of a magnetization. The magnetization orientation of each memory cell assumes one of two stable orientations at any given time. These two stable orientations, parallel and anti-parallel, represent logic values of “1” and “0. ” Supplying a current to a word line and a bit line crossing a selected memory cell changes the magnetization orientation of a selected memory cell by creating two orthogonal magnetic fields that, when combined, switch the magnetization orientation of the selected memory cell from parallel to anti-parallel or vice versa.
However, switching of the memory cells is not always reliable. Sometimes, the combined magnetic fields might not cause a memory cell to switch reliably from parallel to anti-parallel, or vice-versa. This problem is typically solved by increasing crystal anisotropy, coercivity or aspect ratio of the memory cells.
However, increasing the crystal anisotropy, coercivity or aspect ratio leads to another problem: the amount of current for switching the memory cells is increased. Increasing the amount of current increases the amount of power consumed by the MRAM device. In addition, increasing the amount of current requires larger bit lines, word lines, and write circuits to handle the higher currents, resulting in a larger, more expensive, MRAM device.
Therefore, a need exists to improve reproducibility or reliability of switching MRAM devices without increasing the switching current.